Circuit controlling device



Aug- 4, 1959 R. L. PEEK, JR 2,898,422

CIRCUIT CoNTRoLLINC DEVICE Filed sept. 2e, 1957 A TTOR/l/EW Jaya-vUnited States Patent CrnCUrr coNrRoLLING DEVICE Robert L. Peek, Jr., NewYork, N.Y., assignor to Bell Telephone Laboratories, Incorporated, NewYork, N.Y., a corporation of New York Application September 26,1957,Serial No. 686,509

9 Claims. (Cl. 20D- 93) This invention relates to circuit controllingdevices and more particularly to reed type switches or relays of thetype disclosed in Patent 2,289,830, granted July 14, 1942, to W. P.Elwood.

Switches of the type disclosed in the noted patent comprise in general amagnetic flexible member or reed which serves as one Contact and asecond magnetic member which maybe rigid or iiexible and serves as asecond contact, the two members being related so that in response to amagnetic field produced as by energization of a signal coil, the firstmagnetic member or reed moves relative to the second, thereby to effectengagement or disengagement of the contacts.

Important among the criteria for evaluation of such devices are physicalsize, sensitivity of operation, stability in both the operated andunoperated states, and facility of assembly.

One general object of this invention is to improve the performancecharacteristics of reed type switches or relays.

Another general object of this invention is to simplify the structureand facilitate the manufacture of such switches or relays.

It is a specific object of the invention to provide a compact reed typeswitch or relay that requires no mechanical bias and operates whollymagnetically.

It is another specific object of the invention to provide a reed typeswitch or relay of economical construction that has positive switchingaction and which is highly insensitive to shock and vibration.

It is still another specific object of the invention to provide a sealedtransfer contact switch that is small, reliable, sensitive, fast, andeasy to fabricate.

In one illustrative embodiment of this invention a transfer switchcomprises a pair of magnetic contact members and a flexible magneticmember or reed extending between the Contact members. The elementsrecited are mounted in cooperative relationship within a hermeticallysealed envelope which is encompassed by a signal coil.

According to one feature of the invention a permanent bar magnet servesas one of the contacts of the switch and a nonmagnetic metal is coatedon both contacts and the reed member of the switch.

According to another feature of the invention, the permanent bar magnetprovides positive back contact force for the switch and maintains thereed member in a stable position during the runoperated condition of theswitch.

According to still another feature of the invention, a signal coil isarranged to provide a fiux in the operated condition of the relay whichopposes or nullities the permanent magnet field whereby the reedpositively engages the other contact member without the necessity ofmechanical bias.

These and other features of the invention will be more fully apprehendedfrom the following detailed specifi v ments.

ICC

cation taken in conjunction with the appended drawing in which:

Fig. 1 discloses a perspective view of an illustrative embodiment of theinvention with the parts broken away;

Fig. 2 indicates the final step in assembling the embodiment of Fig. l;and

Fig. 3 discloses a schematic of the magnetic circuits of the switch.

Referring to Fig. l, the switch consists of a hermetically sealed glassenvelope 1 in which are located two conducting members 2 and 3 at oneend of the envelope, termed the Contact end. A reed member 4 ispositioned at the other end of the envelope, termed the reed end, sothat each face of the reed is adjacent to a conducting member. Thereedmember 4 and conducting member 2 are made of soft magnetic material. Asignal coil 5 encompasses the glass envelope and causes the relay actioninside the envelope, as will Ibe explained in detail hereinafter.

A permanent magnet 6 is .attached to the conducting member 3 to serve asa back Contact. The magnet is further from the Contact end of the tubethan the front contact 7 of the conducting member 2. The reed member 4normally mates with the magnet and it also extends slightly beyond themagnet and overlaps the contact 7. The reed, the front Contact member,and the magnet have plated metal coatings. The inner coating of themembers is silver-plate which provides nonmagnetic separation betweenthe members for satisfactory performance of the switch, as will beexplained hereinafter. The outer coating of the members is a gold flashsince the magnet, reed and front contact are sealed in air and filmformation must be minimized for good contact performance. lf an inertgas were used, as might be employed in some designs, another choice ofcontact material could `be made, .and gold has been chosen herein forpurposes of illustration only.

In assembling the switch, the magnet is first spot welded to theconducting member 3 and the magnet and front contact member arepositioned with reference to each other in the glass envelope 1 by meansof a jig (not shown) while the contact end glass seal is made. Turningnow to Fig. 2, the final step in ,assembling the switch is shown. Theenvelope 1 is held in a -support 10 with the contact end thereof in theupper position. The reed 4 is inserted into the envelope so that itreaches its normal position which is in contact with the magnet andoverlapping the contact 7. The reed is held in this position by themagnet without the use of jigs or other positioning `devices while thereed end glass seal 11 is made with heating device 12. It will beevident that in the completed structure the reed is properly positionedin its normal position and is free of mechanical strain or bias.Further, the simplicity of construction and ease of fabrication renderthe switch suitable for mass production techniques.

The operation of the switch will now be described lwith reference toFig. 3. In the normal unoperated condition of the switch the reed 4 isin physical and electrical contact with the magnet 6. However, the reedand magnet are separated by small nonmagnetic gaps 13 and 14. Anonmagnetic gap 15 also exists between the reed 4 and the front Contact7 and this gap is relatively large as compared to gaps 13 and 14. Thenonmagnetic gaps comprise the coatings on the elements describedhereinbefore as well as the air gaps' between the ele- The magneticcircuit of the switch has been simplified by representing the coatingson elements 4, 6 and 7 as air gaps.

When the relay is operated and the reed 4 moves away from the magnet 6and makes physical and electrical contact with the member 7, the gap 15becomes small and the gaps 13 and 14 become relatively large.

The magnet field has two principal parts which follow the paths marked Iand II. The field in path I follows an air return path whereas the fieldin path II passes through the gap 13 and the reed 4, and for the mostpart returns to the magnet through the gap 14. A very small portion ofthe field in the path II passes through the air gap 15 and returns tothe magnet through the air path between the magnet 6 and the frontcontact 7 (not shown). Because of the length of the latter air path thefield returning by way of the gap 15 is very small compared to the fieldreturning by way of the gap 14. Hence, in the normal or unoperatedcondition of the switch substantially all of the magnet field passesthrough the gaps 13 and 14 where it exerts forces attracting the reed tothe magnet 6.

In the operated condition of the switch the coil is energized so as toproduce a field in the same direction as that within the magnet 6. Thecoil field predominately follows a path III and it passes through thereed 4 in the sense opposite to the field in path II. As a consequence,the magnet field in the reed is substantially nullified and diverted tofollow path I thereby decreasing the field in the gaps 13 and 14. Asthis occurs, the coil field in gap 15 increases so that at apredetermined level of coil energization the pull at the contact member7 eX- ceeds the opposite pull of the fields in the gaps 13 and 14. Thereed, as a result, moves from the magnet to the contact member 7 and isheld there by the field through the now shortened gap 15 while the coilis energized.

Deenergization of the coil destroys the field of path III, and themagnet field in path II then restores the reed to the normal position.As the reed moves, the gaps 13 and 14 become smaller and the field inpath II increases at the expense of the field in path I. Consequently,the pull on the reed increases as it approaches the normal position.

The nonmagnetic coating on the reed and magnet serves to limit the fieldin the path II during operation of the switch. The nonmagnetic coatingon the contact member 7 serves to keep the field in gap 15 small upondeenergization of the coil. Thus, the coatings contribute to the properperformance of the switch.

it will be noted that the coil field substantially nullifies andreplaces the permanent magnet field or, in effect, the coil field shuntsout the permanent magnet field. In contrast, the coil field of prior artdevices serially combines with at least one or more permanent magnetfields in combination with mechanical bias to effect a switching action.Thus, in the present invention, a single permanent magnet and signalcoil accomplish switching action Without the aid of mechanical bias. Thepresent invention, therefore, provides a small and compact relay whichis of economical construction and less expensive to manufacture thanprior art transfer relays of the reed type.

Since the reed is moved by the coil and the permanent magnet fieldsonly, the switch does not require mechanical bias. Further, the magneticfields of the switch positively position the reed in both the operatedand unoperated conditions, so that the relay is relatively insensitiveto shock and vibration.

The invention offers a number of convenient means for controlling thesensitivity of the switch during and after manufacture. For example, thethickness of the nonmagnetic coating, and the overlap of the frontcontact are factors which may be readily controlled during manufacturefor desired switch sensitivity. The use of metal shielding members onthe coil 5, as is well known in the prior art, would reduce thereluctances of the air return paths or effectively shorten such pathsthereby offering other possible means for controlling the sensitivity ofthe switch. It has also been determined that positioning the coil 5 sothat the magnet 6 and contact 7 are covered thereby also improves thesensitivity of the switch.

Finally, the stiffness of the reed and the force of the magnet areamenable to ready control during manufacture whereby desired speed,contact force and sensitivity can be realized. After assembly of theswitch, the magnetization of the permanent magnet may be adjustedthrough energization of an appropriately poled coil disposed about themagnet, thereby further controlling the characteristics of the relay.

In summary there has been disclosed herein a reed switch having a novelconfiguration and magnetic circuit for accomplishing switching action.The switch is of small physical size and readily fabricated inmanufacture. The operation of the switch is improved in that it ispositive, highly insensitive to shock, and requires no mechanical bias,as the switching is performed wholly magnetically. Also, the sensitivityof the switch is amenable to control during and after manufacture.

It is to be understood that the above-described structure isillustrative of the application of the principles of this invention.Numerous other modifications of the structure may be devised by thoseskilled in the art without departing from the spirit and scope of theinvention.

What is claimed is:

l. A circuit controlling device comprising a rigid magnet, a magneticmember fixed at one end and having a portion normally mating with saidmagnet, the return field path'of said magnet passing through the member,a magnetic contact member in cooperative relation with said member, andmeans for substantially nullifying the return field through said memberwhereby the member moves relative to said Contact;

2. A circuit controlling device comprising a bar magnet having poles atopposite ends of one major face thereof, an unbiased magnetic reed fixedat one end and having a portion spaced from said end normally matingwith said major face, said reed being magnetically separated from saidmagnet, the return field path of said magnet passing through the reed, amagnetic contact facing the face of said reed opposite said major faceof said magnet, and means for substantially nullifying the return fieldthrough said reed, whereby the reed moves relative to said contact.

3. A circuit controlling device comprising a bar magnet having poles atopposite ends of one major face thereof, a magnetic reed xed at one endand having a portion spaced from the other end normally mating with saidmajor face, said reed lying in the return field path of said magnet, amagnetic contact facing the face of said reed opposite said major faceof said magnet, said reed, magnetic contact and magnet being coated witha nonmagnetic material, and means for substantially nullifying thereturn field through said member whereby the member moves relative tosaid contact.

4. A circuit controlling device comprising an unbiased magnetic reedmounted at one end thereof, a magnetic contact opposite one face of saidreed and overlapping the other end of said reed, a bar magnet oppositethe other face of said reed and normally mating with said reed at aposition spaced from the other end of the reed, said magnet, contact,and reed being coated with a nonmagnetic material, and a signal coilencompassing said reed, magnet, and contact whereby energization of thecoil causes the reed to move relative to said contact.

5. A circuit controlling device comprising an unbiased magnetic reedfixed at one end, a bar magnet having p oles at opposite ends of onemajor face thereof, said major face normally mating with one side ofsaid reed at a first predetermined distance from the unfixed end of saidreed, the return field of said magnet passing through the reed, amagnetic member facing the other side of the reed and overlapping theunfixed end of the reed for a second predetermined distance, the secondpredetermined distance being less than the first predetermined distance,said magnet, magnetic member, and reed being coated with a nonmagneticmetal, and means for substantially nullifying the return field of themagnet whereby the reed moves relative to the contact.

6. A circuit controlling device comprising an unbiased magnetic reedfixed at one end, a bar magnet having poles at opposite ends of onemajor face thereof, said major face normally mating With one side ofsaid reed at a position spaced from the unxed end of said reed, amagnetic member facing the other side of the reed and overlapping theunfixed end of said reed, the return field of said magnet passingthrough the reed, said magnet, magnetic member, and reed being coatedwith both a nonmagnetic metal and an oxidizing resistant metal, and asignal coil encompassing said magnet, reed and contact wherebyenergization of the coil causes said reed to move relative to saidcontact.

7. A circuit controlling device comprising an unbiased magnetic reedfixed at one end, a bar magnet having poles at opposite ends of onemajor face thereof, said major face normally mating with one side ofsaid reed at a position spaced from the unfixed end of said reed, amagnetic contact facing the other side of the reed and overlapping theunxed end of the reed, said magnet, reed, and contact being coated withboth a nonmagnetic metal and an oxidizing resistant metal, the magnet,reed and contact being mounted Within a sealed vessel, and a coilsurrounding the vessel and encompassing the magnet, reed, and contact`whereby energization of the coil causes the reed to move relative tothe contact.

8. A circuit controlling device comprising a bar magnet having anonmagnetic plating thereon, an unbiased magnetic member having anonmagnetic plating thereon, said member being fixed at one end andhaving a portion of one face thereof in physical contact with saidplated magnet, the member and magnet being magnetically separated bysaid plating, the return field path of' the magnet passing through themember, a magnetic contact having a nonmagnetic plating thereon andoverlapping the other face of the member, and a signal coil encompassingthe magnet, member, and contact whereby energization of the coilnullifies the return through the field member and causes the member tomove relative to the magnet.

9. A circuit controller comprising a support, spaced parallel electrodesof magnetic material secured to one end of the support, one of saidelectrodes including at its free end a bar magnet extending beyond tneother electrode toward the other end of the support, a flexible reedsecured to said other end of the support in generally parallel relationto said electrodes and having a portion adjacent its free end attractedby and in electrical contact with the magnet and overlapping but spacedfrom said other electrode, the interfaces of the bar magnet, the reed,and the other electrode each having a nonmagnetic conducting layerthereon, and an operating magnet means, which, when activated provides amagnetic field through the reed and said other electrode, said fieldbeing `in a direction to oppose the bar magnet eld in the reed wherebythe reed is released from the magnet and attracted to said otherelectrode.

References Cited in the file of this patent UNITED STATES PATENTS12,245,391 Dickten `lune l0, 1941 2,264,022 Ellwood Nov. 25, 19412,289,830 Ellwood July 14, 1942 2,332,338 Peek Oct. 19, 1943

